Fuel supply system

ABSTRACT

A fuel supply system includes: a flange mounted at an upper opening in a fuel tank; a fuel pump that discharges fuel in the fuel tank; a high-pressure filter that filters fuel discharged from the fuel pump; and a filter case that accommodates the high-pressure filter and includes an upper case and a lower case, the upper case integrally formed with the flange. The fuel pump is fitted to an underside of the lower case to be positioned substantially coaxial with the high-pressure filter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2007-057516, filed on Mar. 7, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fusel supply system for feeding under pressure fuel within a fuel to injectors of an internal combustion engine of a vehicle, and more particularly to a structure capable of improving a mounting property to the inside of the fuel tank and an antivibration property.

2. Description of the Related Art

In order to capture foreign matters such as dust contained in fuel for stable supply of the fuel to, for example, injectors of a fuel injection system mounted on an engine, foreign matters contained in fuel within a fuel tank are firstly removed by a suction filter made of, for example, a nylon mesh material having relatively rough meshes, and then, foreign substances including foreign substances having passed through the suction filter and dust resulting from wear of a brush, a commutator and the like which form a motor unit of the fuel pump are captured by a high-pressure filter such as a filter element made of paper provided downstream of the fuel pump (that is, next stage of the fuel pump along a fuel flow path).

Since the suction filter is located in a so-called upstreammost position in a fuel supply line, the suction filter is generally located in a lowest bottom portion of the fuel tank so that fuel still can be supplied even though fuel remaining with the fuel tank is reduced. On the other hand, in many cases, the high-pressure filter is provided on a flange of the fuel supply system, that is, directly underneath an upper side of the fuel tank so as to send fuel discharged from the high-pressure filter to, for example, a discharge pipe provided on the flange without any delay. Namely, as long as the fuel supply system can be accommodated within the fuel tank having a limited height dimension, it is conceivable that the fuel supply system is provided within the fuel tank to occupy the whole of the height dimension (for example, see JP-B-3256973 (from line 9 in a right-side column on page 3 to line 49 in a left-side column on page 4, FIG. 1); hereinafter referred to as Document 1).

As shown in FIG. 1 of Document 1, since a fuel pump having a relatively large capacity is used, the fuel pump and a high-pressure filter overlap each other, that is, the fuel pump is accommodated within an inner circumference of the high-pressure filter which is formed substantially into a C-shaped configuration (a filter housing in Document 1; and hereinafter referred to as a housing). Therefore, a clearance between an opening in an upper side of a fuel tank and the housing becomes extremely small. Consequently, when accommodating the fuel supply system within the fuel tank, an edge portion of the opening in the upper side may contact with the housing, which may result in fuel leakage from the fuel tank due to a damage made as a result of the contact.

In view of a main feature of Document 1, by dividing the housing into a first housing (a lid) and a second housing (a lower housing) and, furthermore, into an insulating part and a conductive part, a feeding pin can be insert molded in the lid and static electricity can be discharged from the lower housing. As a result, however, a lower housing is required to cover the height dimension of the filter element, and this means that a welding portion between the lid, which prevents the leakage of fuel, and the lower housing has to lie in the vicinity of a root portion where high stress is highly possibly expected to occur. In general, the strength of the welding portion of resins tends to be lower than the strength of matrix resins, and because of this. Therefore, in case strong vibrations generated while the vehicle is being driven are applied to the welding portion, the welding portion may cracks and fuel leakage may be caused.

WO2004/073145 discloses a further miniaturized fuel pump. Namely, a yoke included in the fuel pump includes a first cylindrical yoke disposed on an inner circumference of a ring-shaped magnet of a rare earth and a second cylindrical yoke provided on an outer circumference of the first cylindrical yoke, whereby even with a magnet of a rare earth of a high holding force which requires a strong magnetizing force, the degree of freedom in configuring a magnetic circuit by the magnet and the yoke increases, and the miniaturization of a magnetizer for the magnet and, hence, the reduction in the axial size of the fuel pump are able to be attained. An object of the invention is to provide a fuel supply system in which no fuel leakage is caused from not only the welding portions but also a filter case that accommodates a filter element therein by using a shortened fuel pump.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided a fuel supply system including: a flange mounted at an upper opening in a fuel tank; a fuel pump that discharges fuel in the fuel tank; a high-pressure filter that filters fuel discharged from the fuel pump; and a filter case that accommodates the high-pressure filter and includes an upper case and a lower case, the upper case integrally formed with the flange, wherein the fuel pump is fitted to an underside of the lower case to be positioned substantially coaxial with the high-pressure filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a fuel supply system according to an embodiment of the invention;

FIG. 2 is an exploded perspective view of the fuel supply system in FIG. 1; and

FIG. 3 is a sectional view of a fuel pump in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a fuel supply system 101 includes: a flange 1 that is formed from an insulating resin and integrally molded to include an upper case 1 a that incorporates therein an element that forms a high-pressure filter (described later); a lower case 2 made from an insulating resin to be secured to the upper case 1 a through heat plate welding; a pump holder 3 engaged with the lower case through, for example, snap-fit and to hold therein a fuel pump (described later); and a suction filter 4 inserted from an opening in the pump holder 3 so as to be fitted to a suction port of the fuel pump. In addition, while reference numeral 1 c denotes a connector molded integrally with the flange 1 for supplying electric power to the fuel pump, the illustration of lead wires that are provided to extend from the connector 1 c are omitted. In addition, a filter case 5 is formed by the upper case 1 a and the lower case 2.

An assembling procedure of this fuel supply system 101 will be described with reference to FIG. 2. An element 6 is inserted in the upper case 1 a. The element 6 is obtained by mounting a member 6 b on an outer circumference of an inner tube 6 a. The mounting member 6 b is obtained by forming a sheet of a material, such as resin fibers of polyester added to pulp, around an axis of the inner tube 6 a in a chrysanthemum-like fashion. The inner tube 6 a has upper and lower collar portions and which is formed from a conductive resin. An axial dimension of the upper case 1 a is equal to an overall length of the element 6. Namely, when the element 6 is inserted into the upper case 1 a and the upper collar portion of the inner tube 6 a abuts on a ceiling of the upper case 1 a (in other words, a bottom side of the flange 1), a lower end face of the upper case 1 a and a projecting surface (formed into a convex shape and not shown) of the lower collar portion of the inner tube 6 a become flush with each other. On the other hand, upper end faces of the lower case 2 for respectively receiving surfaces of the lower end face and the projecting surface also become flush with each other. Namely, as described above, the filter case 5 is formed by securing both the upper case 1 a and the lower case 2 together through heat plate welding, and as this occurs, since the inner tube 6 a and the lower case 2 are also welded together at the same time, the element 6 also comes to be secured.

In securing the element 6, in the event that for example, a terminal member of a conductive resin (not shown) is attached in advance to the lower case 2 to be exposed from an outer surface of the lower case 2, the projecting surface is welded to the terminal member, and by drawing an earth wire from this terminal member, static electricity generated in the element 6 can be discharged. In addition, although a lower end of the inner tube 6 a is closed by virtue of the securing of the element 6 in the way described above, since an inner wall of the lower case 2 forms a through hollow space and a space is formed between an inner wall of the upper case 1 a and the element 6, fuel is allowed to flow into the element 6. In addition, a plurality of communication holes which establish a communication between the inside and outside of the inner tube 6 a are provided in the vicinity of a lower portion of the upper collar portion of the inner tube 6 a, and the inner tube 6 a communicates with the discharge pipe 1 b. Therefore, a fuel path is secured from a discharge pipe of the fuel pump to the discharge pipe 1 b.

An opening 3 a is provided in a bottom side of the pump holder 3, and a recess portion is formed to match the configuration of a bottom portion of the fuel pump 7 (see FIG. 3), whereby when the fuel pump 7 is inserted into the pump holder 3, the fuel pump 7 comes to be held in a predetermined position within the pump holder 3. In addition, since a suction port 21 a of the fuel pump 7 is positioned in the opening 3 a, a connecting portion 4 a of the suction filter 4 is connected to the suction port 21 a, whereby fuel inside the fuel tank (not shown) is sucked by the fuel pump 7 via the suction filter 4.

A fuel suction port 2 a is provided in the lower case 2, and this fuel suction port 2 a is securely fitted on a discharge pipe 15 a of the fuel pump 7 via a connecting pipe 8 when the lower case 2 is engaged with the pump holder 3 through snap-fit in the way described above, whereby the fuel supply system 101 is completed, that is, a fuel flow path from the suction filter 4 to the discharge pipe 1 b is completed. By inserting the fuel supply system 101 so completed from an opening in an upper side of the fuel tank (not shown) the opening in the upper side of the fuel tank is closed by the flange 1, and fuel inside the fuel tank is pressurized by driving the fuel pump 7 and supplied to injectors of a fuel injection system via a fuel hose (not shown) that is connected to the discharge pipe 1 b.

Next, the fuel pump 7 and driving thereof will be described with reference to FIG. 3. As shown in FIG. 3, the fuel pump 7 includes the motor portion 10 and a pump portion 20. In the motor portion 10, a magnet 13 of a cylindrical shape is disposed on an inner circumferential surface of a yoke 11 to be spaced at a predetermined distance from an outer circumferential surface of an armature 12. Together with the yoke 11, the magnet 13 forms a magnetic circuit at an outer circumference of the armature 12. In addition, the yoke 11 includes a first cylindrical yoke 11 a and a second cylindrical yoke 11 b, which are made of an STKM (a carbon steel pipe for machine structure), in which the first cylindrical yoke 11 a is press fitted in the second tubular yoke 11 b from an axial direction until the first cylindrical yoke 11 a comes into abutment with a projecting portion 11 c of the second cylindrical yoke 11 b.

By being bent toward an axial center of a shaft 14 at both end portions, the second cylindrical yoke 11 b integrates the following components together which include a bearing holder 15, an inlet housing 21 and an outlet housing 22. In addition, the bearing holder 15, which is formed of an insulating resin mainly made of polyacetal, accommodates therein a check valve 16, a bearing 17 which supports the shaft 14, a conductive brush 18, a coil spring 19 which pushes the brush 18 against a commutator 12 a, a lead wire 18 a which supplies a current to the brush 18 through a connector 1 c (refer to FIG. 1) and the like.

As for the pump portion 20, a shaft stopper 23 is accommodated in the inlet housing 21, which is formed from a resin, and the inlet port 21 a is formed in the inlet housing 21. The outlet housing 22 is also formed from a resin, and a discharge port 22 a is provided therein for discharging fuel which is pressurized in a flow path 24 toward the armature 12, and a bearing 25 which rotatably supports the shaft 14 is also accommodated in the outlet housing 22. A D-cut portion 14 a formed into a D-shape in cross section at an end portion of the shaft 14 is fitted in a D-shaped hole in a central portion of an impeller 26 formed from a resin and having a plurality of blade grooves formed on an outer circumference thereof. The flow path 24 is formed by the plurality of blade grooves on the impeller 26 and recessed grooves 21 b, 22 b respectively formed on the inlet housing 21 and the outlet housing 22.

Next, the operation of the fuel pump 17 will be described. When current is supplied from the battery (not shown) to the armature 12 via the connector 1 c, the lead wire 18 a, the brush 18 and the commutator 12 a, the armature 12 rotates together with the impeller 16 on the shaft 14 as a rotational shaft based on the principle of direct current electric motor. In conjunction with the rotation of the impeller 26, fuel within the fuel tank is introduced to the suction port 21 a after foreign matters contained therein have been removed at the suction filter 4. Then, the fuel is pressurized within the flow path 24 and passes through the discharge port 22 a, thereby entering a space within the motor portion 10. When flowing through a space between the armature 12 and the magnet 13 inside the motor portion 10, the pressurized fuel cools the armature 12 and causes the check valve 16 to open so as for the fuel to be discharged from the discharge pipe 15 a. The discharged pressurized fuel is introduced into the element 6, where foreign substances including foreign matters having passed through the suction filter 4 and dust resulting from wear of the brush 18 and the like are captured, and is thereafter supplied to injectors of the fuel injection system. These are the summary and configuration of the fuel supply system of the embodiment.

Although not described in detail, since in particular, the axial length of the fuel pump 7 is suppressed as much as possible, as shown in FIG. 1, even in the event that the element 6 and the fuel pump 7 are arranged in series in the vertical direction, when compared with the conventional fuel supply system, the overall lengths of the two systems differ little from each other. Then, the filter case 5 is streamlined, or more specifically, an outside diameter thereof is made equal to or smaller than that of the pump holder 3, and the filter case 5 and the pump holder 3 are provided so that axial centers thereof are aligned substantially coaxially. Consequently, a difference in outside diameter between the flange 1 and the filter case 5 can be increased without increasing (changing) the outside diameter of the flange 1. This means that a sufficient clearance can be secured between the opening in the upper side of the fuel tank and the filter case 5 without expanding the opening more than required. Therefore, when assembling the fuel supply system 101 into the fuel tank, a damage to the filter case 5 can be prevented which would otherwise be made due to contact between the edge portion of the opening in the upper side of the fuel tank and the filter case 5, hence, a fuel leakage from the damaged portion can be prevented.

In addition, since the filter case 5 is formed by welding the upper case 1 a and the lower case 2 together, there occurs neither fuel leakage from the securing portion where the upper and lower cases are secured to each other through such welding nor reduction in fuel pressure due to such a fuel leakage. Furthermore, in the embodiment, since static electricity generated when the pressurized fuel passes through the element 6 is discharged via the inner tube 6 a, an inexpensive insulating resin is used for the upper case 1 a having a relatively large surface area, and since the upper case 1 a is formed integrally with the flange 1, as described above, the securing portion resulting from the welding is provided below the element 6. Namely, since the securing portion is spaced apart from the root portion so that generation of stress is reduced remarkably, the inexpensive fuel supply system can be provided which is free from fuel leakage from the securing portion which would otherwise be caused due to vibrations being applied thereto.

Furthermore, when forming (welding) the filter case 5, since the lower end face of the upper case 1 a is flash with the projecting surface of the lower collar portion of the inner tube 6 a, and the upper end faces of the lower case which respectively forms the receiving surfaces of the lower end face and the projecting surface are also flush with each other, the so-called heat plate welding becomes possible, whereby in conjunction with the fact that the formation of the filter case 5 is implemented at the same time that the element 6 is fixed, the production costs can be expected to be reduced. In addition, in this embodiment, although a pressure regulator used to maintain the pressure of fuel in supply thereof is not included, such a pressure regulator is not necessarily attached to the fuel supply system or is not necessarily an element in the fuel supply system. Instead, a method may be adopted in which a pressure regulator is provided outside the fuel tank and between the discharge pipe 1 b and the injectors, and a pipe for excess fuel therefrom is inserted into the fuel tank. 

1. A fuel supply system comprising: a flange mounted at an upper opening in a fuel tank; a fuel pump that discharges fuel in the fuel tank; a high-pressure filter that filters fuel discharged from the fuel pump; and a filter case that accommodates the high-pressure filter and includes an upper case and a lower case, the upper case integrally formed with the flange, wherein the fuel pump is fitted to an underside of the lower case to be positioned substantially coaxial with the high-pressure filter.
 2. The fuel supply system according to claim 1, wherein an abutment position between the upper case and the lower case is arranged below the high-pressure filter.
 3. The fuel supply system according to claim 1, wherein an abutment position between a lower end face of the upper case and an upper end face of the lower case and an abutment position between a lower end face of the high-pressure filter and the upper end face of the lower case are at the same height.
 4. The fuel supply system according to claim 2, wherein the filter case is formed by welding at the abutment position. 